Racket and method of manufacture of the same



H. W. HALL Nov. 10, 1931.

RACKET AND METHOD OF MANUFACTURE OF THE SAME Filed Dec. 27, 1926 .Horwce ZdHw ll 1 1,, mammciuamu 41m:

Patented Nov. 10, 1931 UNITED- STATES PATENT; OFFICE HORACE w. HALL, OF NEWTON; MASSACHUSETTS, ASSIGNOR, BY MESNE ASSIGNMENTS,

. TO DOROTHY K. HALL, OF NEWTON, MASSACHUSETTS nacxn'r AND METHOD or MANUFACTURE or ran sum Application flled'necember 27, 1926. Serial No. 157,059.

lightness in the head, and yet produce rackets which are stronger and stiffer than any rackets heretofore produced and able to take the tightest stringing without pulling the head out of shape. Likewise, this invention produces rackets in multiple production with uniform weight and balance at a low cost, zo unobtainable in the present methods of racket vmanufacture, and eliminates, as far as it is possible to eliminate, warping and twisting tendencies. Among the features of this later-invention is the discovery of classes of 25.1ight and heavy, strong woods, which when.

combined, will act similarly in expansion and shrinkage under atmospheric changes; also a combination of woods of small co-eificient of shrinkage and expansion; the alternate arrangement in the bow of thin laminae of strong and light weight .woods of distinctly different color; the making and insertion of the throat in different sections andat different periods in the construction of the racket frame, the outside sections being assembled and glued to the bow when the laminated bow is constructed and the insertion and gluing of the center section or sections of the throat,

Y after the bow has taken its permanent racket shape and the glue set the composition of the throat being of different woods adapted to end wood gluing and the center section either single or multiple made of stiff, strong material; the different segments of the throat laminated longitudinally, the glue joints running at right angles to the plane of the racket face; and the insertion of light and heavy woods, or other material between the bow part in the handle portion of the racket, ar-

,tion of the bow with first two elements of the v throat piece;

\ Figure 2 is a perspective representing the product thus made in multi-frame widt Figure 3 is a perspective indicating the next two steps in manufacture, viz: the completion of the'throat and handle, and the severing into frame width for individual rackets Figure 4 shows on a lar er scale a fragment of the bow, indicating t e arrangement of laminae therein and reveals the color contrast; Figure 5 is a diagram for the cutting of a detail from stock; and i Figure 6 is a detail of head and throat po 'tion of finished racket showing the three segments of throat piece as they appear in the finished racket, revealing by the color contrast the position of the strong center ply in relation to the center axis 0 play. 30 Referring to the drawings, which illustrate the embodiment of the invention which I. at present prefer, and speaking first of the construction and afterwards of the material whose selection and combination contribute to the production of the improved result afforded by the invention, the diagram in Figure 1 indicates the formation of a racket bow in a suitable press wherein laminae of wood suitably selected and arranged are coated with glue on their proximate surfaces and then are shaped by pressure, indicated by the arrows, between steel cauls 12, 12, 14 and 16, of which 12 is a central caul having the shape in which the bow is to be made except at the throat where it has a strai ht extension 12' running down through t e throat and the handle; The pressure applied to a the laminae should first be applied to the crest 'of the head of the bow, and then progressivel 1y at points along the sides toward the handle, thus makmg a smooth, close joint all the way. Using material of width sufiicient,

to make a considerable number of racket frames from a single preliminary broad formation, the result of the steps thus far descr bed is the production of a broad bow in wh ch the two side portions 20 of the throat, WhlCl]. are of light weight wood with good end wood gluing properties like mahogany,

ter throat section; 24: preferably a cheap light weight wood or other light weight material is positioned in the middle portion of i the handle or this space may be left vacant and, 26, of heavy or light weight wood depending on balance required (light or heavy in head) may be put at the end of the handle,

the handle and throat being then glued together with the filling pieces in their described positions between pressure blocks, 28. As there are no curved surfaces in this gluing process, only the simplest kind of pressure device is needed, the pressureworking only in one direction, as shown by the drawings. In ordinary methods two steps. are taken in the gluing in of the throat and handle plug. Ordinary throat gluing requires both side pressure andvertical pressure. Vertical pressure is necessary in order to keep the throat from slipping towards the headof the racket, due to the curved gluing .sur-

. face of the solid throatpiece, and the handle plug 'is generally glued in later. In my invention part of the throat is glued in with the same apparatus and at the same time as the bow part is glued up, which is one process, and the balance of the work, namely the insertion and gluing of the center throat section and center handle sections represent the second and final process which requires only the simplest side pressure, as the gluing surfaces are flat and strai ht, running longitudinal to the long axis 0 the racket.

In the ordinary method of racket production the tennis racket has been made by softeningthe racket stick and bending the same to required racket shape and allowing it to dry and take its permanent shape before the throat piece is inserted and glued to the same.

This has resulted in failure of the glue joint between the bow andthroat piece, due to uneven contraction of the bow wood in drying,

thus making an imperfect fit in the curved overcomes. Multiple production requires the use of the bending machines for new frames at frequent intervals. Thus, the frames must be released before the glue joints are hardened and the material is dry. These weaknesses result in a separation of the throat from the bow due to the fact that when the pressure is released at the throat section, the bows tend to spring away from the solid throat on either side, and although the frames may be immediately put under pressure for the drying period, the damage has occurred and inevitably shows up when the rackets are finished. With this invention the center section of the multiple ply throat piece is left out for the purpose of allowing an expansion joint.

the simplest side clamps being required, thus insuring'a high percentage of perfectframes with lowest cost production, in which the throat is a feature of strength, lightness and rigidity, heretofore unobtained. After this the multiple frame is severed 1nto many single frames 10" as indicated by dotted lines in Figure 3, each unit of which is thereafter to be suitably finished, including face and back covers (not shown in Fig. 6) for. the handle, ready for stringing (Figs. 4, 6).

7 Important additional advantages are attained by having the throat jplece made of different woods of different density and color Only the side segments of the throat piece are glued to the bow part when the how divided longitudinally and by having the outer throat sections-20 independently manufactured and glued to the how 10 at the same time the bow is glued up and the center section 22 glued in later after the bow has taken its permanent shape and the glue is set. Among these advantages are, greaterstrength and stiffness in the throat, coupled w1th l1ght-, ness, thus eliminating the clubby feeling so often found-in rackets where aheavy throat is required in order to obtain strength and stiffness. The stiffness and strength here-depend upon the center section 22 being of stiff, strong material acting in the center longltudinal axis of play and the lightness being obplies running parallel to the face of the racket and'primarily constructed for the purpose of having a hard wood inthe center to take the wear of the gut. The throat in my invention is not built for resistance to wear of gut, as I put no wearing strain on it. The wear of the gut is taken up by the outside raw hide pieces and the round ash reinforcement piece 32 on the inside, (shown in Figure 6) which is common to many rackets. The

throat in my invention is primarily constructed and assembled for the'purpose of gaining a stronger and stiffer throat and at the same time reducing the weight. Saving in utilization of material is another advantage; this is shown in Figure 5, wherein the dotted lines 20 indicate the lines of cutting to fit the portion 10' of the curvature of thebow; whereas the cutting'of a full throat, shaped of solid wood, cannot-so completely use'the surface of a block, In my invention the difficulties which attend the shaping of a multiple solid throat piece of great depth for multiplerack et frames are overcome, as my multiple throat piece is made in three sections, independently manufactured and independentlyglued'to the bow portion. This eliminates considerable waste and degradation of frame. The ordinary multiple solid throat piece is often spoiled by working down a little bit too far its outside curved portions where they join the straight section, thus eating into the straight section and spoiling the symmetry" 7 of the piece, making a perfect fit impossible,

resulting in a-poor glue joint at this point,

and, therefore, a second grade frame.

, Other features of the invention reside in the selection, arrangement and combination of klnds of wood 1n the frame.

In my pending application, Serial f No.

. 70,530-which has become Patent 1,682,504, I have disclosed and claimed a method of using and combining laminae of diverse kinds of wood; strong, hard, dense wood, which inci-' dentally is heavy, and light wood, which 'inci-- clentallyis softer and weaker, yet stronger in proportion to its weight than is the heavy wood, in'order to produce'a racket whose head has strength,"lightness and caring ualities in high degree. I now-disclose furt er improvements in the structure of the bow. I

have discovered that the selected woods should be such that the co-eflicient of contraction commonly called shrinkage? of-the Strength is' which make up the bow. Likewise, the woods" should be selected for small total volume shrinkage. Likewise, I select woods of striking difference in color. I have in this respect found birch satisfactory for the strong, hard, dense wood and magnolia for the light wood. And I find there is advantage in arranging the laminae of each kind of wood alternately through the bow. Inan improved example 4; I use nine laminae of which five are' birch and four are magnolia, with the extreme outer and innerlaminae being of birch. Such a bow has outer and inner surfacesof the stronger and harder wood, also has the third layer from the outside, of the stronger and harder wood to take the wear of the sunken loops of gut, and has the lightness with relatively greater strength which I results from the use of lighter laminae. This permits the making of the frame of greater depth, in

which caseits strength increases in greater ratio than does its depth. The effect of selecting the wood as seatedis that the glued joints are more perfect, for, the glue having dried in a few hours while'the wood' requires a number of days for thorough drying, the conranged, or. a laminated racket .in which the strong dense wood or the lightweight wood.- This is contrary to what would naturally be expected and is due to several factors:

. First and foremost, because the total volume shrinkage of the less dense wood is always greater than that of the dense wood, due to the greater absorption of moisture from wet glue. With alternate lamin ations, the dense or stronger wood tends to holdthe less dense wood from shrinking, which is almost impossible where all the dense wood is together and all the less dense wood is together, which makes for a greater strain at the joint of union on account of the great body ,of different ply all shrinking together.

Secondly, I have discovered by further investigation that the ordinary hot glues used in tennis manufacture cannot be successfully bow is built up of all one wood whether the rackets.

tained in any of the hot glues or non-waterproof glues; and I have found no waterproof glue that will serve all "requirements, when used as is customary in putting together plywood, as for example, with pressure of fifteen to twenty-five pounds per square inch.- But by using a cementing material of such nature that when soft it can be forced under pressure into the interfibrous spaces of the wood, or into the wood cells (as for example a cementitiou's substance of which casein is an illustration which althou h commonly called a colloid may be had in a form which is more like what is typical for crystalloids than like what is typical for colloids as to its osmotic power of diffusion, and specifically so as to the capacity for penetrating wood) and by the application of extremely high pressure,

' a combination of materials at the joint may be made producing a structure comparable to that of reinforced concrete in that there is at the joint, after the casein has hardened to its horn like consistency, a mass composed as a whole of the hardened penetrating cement or glue and the said fibres in its midst, with the wood fibres lying through all parts of this mass an'dathereby reinforcing and strengthening the cohesive power of the glue, without there being any substantial body or plane film of glue between laminae which is devoid of this reinforcement and whose native brittleness might therefore lead to a fracture under the shock of severe play. Alternate lamina tions of dense and less dense wood favor the obtaining of this effect with such a cementing material, as the wood fibres of adjacent surfaces, especially when softened by the liquid cement, can readily be forced into each other.

This is not so much the case when all dense .hardwood is used; But the soft wood being intimately close to the hard wood gives a chance for the intermeshing of fibres of the adjacent laminae to occur. When the cement hardens these interlocked fibres are rigidly held in place and the wood cells adjacent to the joint are filled'with and surroundedby the cement. No such breakage can now occur in the glue joint, as there is no foreign film separating one lamina from its neighbor, except to approximately the same degree that fibres are separated from other fibres in the same lamina by the cementitious substance permeated therein. I believe it is because of the presence of such a film that I have found even casein to fail under the shock of severe play if the laminae have been put together withonly ordinary pressure but to hold successfully when an applied pressure of one hundred to two hundred pounds per square inch has forced the casein into the adjacent laminae and left tlfe space between them devoid of such a film. With a glue that behaves like a typical colloid the forcing of such a penetration, by pressure applied to the wood, does not appear to be possible, but with a glue such as casein in such a form or conclition that it has the property of osmosis in greater degree, as is possible with casein and other proteins,1I have discovered that this may be accomplished.

A. similar intermeshing offibres may obtained between laminae all of soft wood,

but in this case some special means must be provided to resist the wear of the gut, and to eliminate or resist the shearing tendency at the union of throat and bow, arising be,- cause the thick throat piece does not absorb but a small percentage of the glue and thus in l the process of drying after being glued does not shrink as much as the soft wood of the bow. With the alternate arrangement of hard and soft laminae above described the total shrinkage of the bow is reduced'and the shearing strain at union of bow with throat is therefore almost entirely elimi nated. .There are other factors of advantage in alternate lamination of dense and less dense, strong woods. All uneven strains due to' the inherent difference in physical properties of the difierent woods are uniformly balanced. Likewise, all changes in physical properties due to the impregnation of the cementing material between the ply are uniformly distributed through the composite structure and all later changes due to expansion and contraction from atmospheric conditions, are to a large degree uniformly distributed, and no great strain occurs at any one point. This balance and counter balance of forces is the most difficult part of tennis racket production and to my knowledge has never so far been successfully obtained in conjunction with the factors of lightness, balance, strength and stiffness, both in direction of" play and at right angles to direction of play to take care of tight stringing together with the necessity of a hard wearing material to counteract the cutting .forces of the gut.

The introduction of a. strongwood center section in the throat such as maple with the great body of the throat being composed of light weight wood such as mahogany, not only increases strength but makes a pleasing and unique color contrast and helps material- 1y, thebalance of the racket. The balance in the racket is one of the most difiicult things to control. Heft in the throat makes a clubby feeling racket, always undesirable. This has hitherto been necessary in order to obtain the necessary strength and stiffness at this point and has resulted in the necessity of boring the end of the handle in order to reduce the total weight to the required ounces at the expense of balance, throwing the weight to the head. The present invention because of the lightbow and light throat,

permits the use of a heavy 'wood center at the end of the handle without extra manu- .facturing cost, which throws the weightto the handle and gives the desired light feel and perfect balance for fast tennis play,

, without in any way weakening the product or increasing the total weight of the racket beyond the desirable limit. Also, the construction of frame with color contrast between diifere'nt pieces of wood laminae, and

in the throat, makes it now possible for a. maker to produce racket frames in the rough,

' heretofore.

I claim as my invention r 1. A process for the manufacture of rackets with wood bow comprising the gluing of side sections of the throat filler to the throat portions of the bow when the bow is being I formed; and the subsequent completing of the throat filler by the securing of the said side sections together directly across the media-l plane between the throat portions of the bow, after the bowhas permanently set.

2. A process for the manufacture of rackets with wood bow comprising the forming of the bow with filling pieces thereon. at its throat having cleavage on the medial plane perpendicular to the face of the racket and with space at said cleavage; followed by the inserting of a third filling piece at the throat in said space,'and gluing it therein with pres-- sure wholly perpendicular to said plane.

3. A process in the manufacture of wood bow rackets whereby sections of the throat piece of the racket are glued and set onthe bow part of the racket before being permanently connected to make the throat.

4. A process in the manufacture of' wood bow rackets whereby the bow portion is first forined in what is substantially its permanent racket shape with side sections of the throat glued thereto and then a middle section of the throat is glued to the said side sections.

5AA racket comprising a bowembodying Wood laminae bent to'bow shape, and a throat filler embodying two side members and a central member of substantially uniform thicknss, said side members being united to a curved portion of said bow and terminating above the straight handle portion of said bow, said central member extending below said side'members and being united directly with the laminae forming said straight handle portion.

tral member, said side members being united" at their outer sides to a curved portion of said bow and terminating at their lower ends prior to reaching the straight handle portion, said central and side members being so united and of such shape that the top surface of said filler curves inwardly, the top surface of said central member being even' with the top surfacesof said side members, said central member extending below said side members and being'directly united with the laminae forming said bowfrom the point of termination of said side members and being of substantially the samethickness throughout.

7. A racket comprising a bow, and a throat filler embodying a plurality of side mem bers and a central member united with each other and with said bow, said central member extending below said side members into the handle portion of the bow and being of substantially the same thickness its entire I length.

8. A racket comprising a bow formed from a plurality of wood laminations bent to bow shape, said laminations being of" suflicient length to form both the curved portion and a full length straight handle portion of said bow, and a throat filler embodying two side members and a central member, said central member extending below said side members into said handle portion, and being of substantially the same thickness its entire length.

' 9. A racket comprising a bowand a throat 1 filler embodvingga pluralitv'of side mem bers and a central member united with each other and with said bow. the outer side of said side members being united for their full length with curved portions of said how, said central member extending below said sidemembers into the'handle portion of said bow, the joints formed bv the union of said central member with the side sections of said how being parallel with the longitudinal axis of the racket. v

. 10. A racket comprising a bowformed from a plurality of wood laminations bent to bow shape. said laminations being of sufficient length to form both the curved portion and a full length straight handle portion of saidbow. and a throat filler-embodving two side members and a central member. said central member extending below said side members into said handle portion.

11. A process in the manufacture of a wooden bow racket comprising uniting with glue, side sections of the throat filler which are curved for their full outside length, to

the curved throat portion of the bow, independently of each other and allowing the glue to set. followed by inserting. between said side-sections a filling piece of uniform thickness which is longer than said side sections and uniting a portion of said filling piece to .theinner surfaces of said side sections and" another portion directly to the straight handle portion of the bow.

12. A racket block ready to be cut into individual rackets, comprising a plurality of wood laminations united together which form curved bow and straight handle portions of the racket, a plurality of throat side members united to said how, and a throat central member of substantially the same thickness its entire length extending below said side members, a portion of said central member being between and united to said side members, and another portion being between and united directly to said straight handle portion. v

Signed at Boston, Massachusetts, this 22d day of'December 1926.

HORACE W. HALL. 

